The Multifunctional Assault Rifle - just a dream?

A multi-functional assault rifle is designed to be versatile and adaptable for various combat situations. It typically incorporates features like modularity for attaching different accessories, a variety of fire modes, and the ability to handle different types of ammunition, making it suitable for close-quarters combat, long-range engagements, and even specialized tasks - such as launching grenades or providing bursts of suppressive fire. Originally the term 'assault rifle' was during WWII created to describe a battle rifle capable of both semi- and full-auto fire based around an intermediate-range (600-800 meters) cartridge that bridged the gap between sub-machine guns firing short-range pistol rounds and bolt-action or semi-auto rifles firing powerful long-range cartridges. 

It didn't take long after the Second World War though for armies to realize that caliber sub-machine guns still had a useful role, and that a lightweight automatic rifle also wasn't as effective as a belt-fed light machine gun. There was also still a need for more powerful rifles that could accurately reach out effectively beyond 800 meters as well - filling the so-called 'designated marksman' role. For this reason, NATO continues to field assault rifles in 5.56x45mm caliber and machine-guns and marksman rifles in the larger and more powerful 7.62x51mm caliber. Recent cartridge developments such as the 6.5x43mm (.264 caliber) round of the FN LICC program and the 6x38mm (.243 caliber) Advanced Rifle Cartridge (ARC) from Hornady have reignited the discussion of whether a standard assault rifle could actually also fulfill the roles of light machine gun and marksman's rifle?

In this guest post by Swiss defense expert Marco Damaso, he references his experiences and provides his thoughts on the matter.

The Multi-functional Assault Rifle: Future Standard or Unrealistic Dream?

Modern infantry squads often carry a mix of weapons – assault rifles, light machine guns, and designated marksman rifles (DMRs). Each excels in its own role, but this diversity comes at a cost: more training requirements, no magazine interchangeability, and more logistical complexity in the field. But what if one weapon could do it all?

In this post, I take a closer look at the multifunctional assault rifle – a single platform designed to combine the firepower, accuracy, and versatility of all three.

My First Encounter with the Concept

When I began my compulsory military service in 1983, I was issued my personal service rifle – the 7.5 mm Sturmgewehr 57 (Stgw 57). It was developed by SIG under the designation AM55 and was later commercialized in various versions as the SIG SG 510.

The Stgw 57 was designed to be a multi-functional assault rifle, with the following capabilities according to the field manual:

• Rifle: effective up to 600m\
• Anti-tank: with shaped-charge rifle grenades up to 100m
• Grenade launcher: shrapnel or smoke rifle grenades up to 250m in direct fire; shrapnel rifle grenades up to 400m in indirect fire
• Bayonet for close combat

Needless to say, the Stgw 57 was not an effective multifunctional assault rifle. 

Here are some observations:

The Stgw 57 was a precise weapon, but with a loaded weight of 6.6 kg, most shooting was done prone on the bipod (in the middle position) or supported (terrain). Unsupported stances were almost never used due to the weight and poor ergonomics.

Moving the bipod to the forward position was intended to better stabilize the Stgw 57 when used as an automatic rifle. In practice, almost no one could keep bursts within the intended 4% dispersion.

The 1.16 kg shaped-charge rifle grenades had enormous (and I mean enormous) recoil, and most shooters were afraid of it, resulting in poor shooting performance. The Stgw 57, however, excelled as an indirect fire launcher with shrapnel filled grenades.

For the record, the negative recoil experiences with the rifle grenades were a decisive factor in choosing a 40 mm grenade launcher for the 5.6 mm Stgw 90 instead of rifle grenades.

Trials by Swiss Special Forces

During my time in the Special Forces Command, I experienced the concept of using an assault rifle as a squad automatic weapon. The advantage of having a lightweight weapon with the same magazines for all weapons in the squad is obvious.

At that time, we were using the 5.56 mm Stgw 07 (SIG SG 553 LB), but its handguard length was inadequate for the LMG role. We conducted trials with a SIG SG 551 LB (longer handguard and 17.8-inch barrel), equipped with a bipod and a 3.5X ACOG scope.

The shooting tests in bursts and rapid single fire were excellent and met the requirements. Unfortunately, the weapon could not sustain the required number of magazines and rate of fire without rounds 'cooking-off' in the chamber because of heat build-up, so the project was terminated.

The US Marine Corps' Approach

So, is the concept of a multifunctional assault rifle feasible? Yes – and, as so often - the US Marines led the way.

In 2010, they fielded the M27 Infantry Automatic Rifle (IAR) as a replacement and supplement for their M249 Squad Automatic Weapons (belt-fed light-machine guns). The M27 IAR is essentially a standard H&K 416 with a 16-inch barrel – the best compromise in barrel length for the 5.56×45mm NATO round – and it met the no-cook-off requirement (36 rounds per minute for 16 minutes and 40 seconds) despite being a closed-bolt system.

In 2017, they introduced the M38 designated marksman rifle, which is basically an M27 IAR fitted with a Leupold TS-30A2 Mark 4 MR/T 2.5–8×36 mm scope.

By 2018, they began transitioning completely away from M4 to the M27, and in 2020/21 they replaced the 3.5× ACOG with the Squad Common Optic (SCO) – the Trijicon VCOG 1–8×28 – and issued the Knights Armament Company (KAC) NT4 suppressor for all M4, M27, and M38 rifles in USMC inventory.

Conclusion

From my experience (and looking at the experience of the USMC), a single, well-designed platform can deliver all three main roles – rifle, squad automatic weapon, and DMR.

The belt-fed light machine gun vs. magazine-fed squad automatic rifle debate will probably never end. But for me, lighter weight, faster reloads, magazine commonality, and precision in single fire outweigh a higher sustained rate of fire – at least on the move. For established defense positions? I’d still take a belt-fed MG.

Most modern assault rifles can serve effectively as squad DMRs. Equipped with a modern LPVO, an assault rifle can provide good, designated marksman capability. Purists will disagree, often because they envision that a DMR should be a “mini sniper rifle.”

Hopefully, this idea will be on the table when Switzerland starts replacing the 5.56 mm Stgw 90 (SIG SG 550) in the coming years.

Follow Marco online here.